The present invention refers to a circuit for providing a minimum wake-up time (xe2x80x9cawakeningxe2x80x9d) in wake-up logic circuits.
An object in the provision of an electronic system is to reduce the power dissipations in a consistent way. A pursuable way to obtain this is to provide that those parts of the system that react to sporadic events are set in a state of stand-by, also called xe2x80x9cenergy saving.xe2x80x9d In order to enable these parts again, a specific signal is used that is generated by a circuitry called xe2x80x9cwake-up circuitry.xe2x80x9d
The function of this wake-up circuitry is to compare the input and output signals of a device to be controlled in a such way that it is possible to detect variations in the state of the device. The wake-up circuitry can also be integrated inside any device of the system, such as a buffer, counters, a shift register, etc., that function as an interface between the aforesaid sporadic events and the rest of the system.
The wake-up circuitry is characterized by two fundamental parameters: (1) minimum input pulse; and (2) minimum duration of the wake-up signal.
The minimum input pulse represents the minimum time length that a variation of the input state of the wake-up circuitry must have in order for said circuitry to generate the wake-up signal.
The minimum duration of the wake-up signal represents the minimum time length that the wake-up signal must have once it has been enabled, that is once the wake-up signal is brought to a low logic level. Once this minimum time has elapsed, the signal will return to the initial state, that is to a high logic level, when the inputs and the outputs of the device being controlled become equal again.
Known circuit solutions have the problem that once the minimum time in which the signal must be enabled has elapsed, that is at a low logic level, said signal shows a time delay in going back to the initial state, that is when the inputs and the outputs of the device being controlled coincide again.
In view of the state of the art described, the disclosed embodiments of the present invention fulfill the second parameter that characterizes the wake-up circuitry, providing a minimum duration wake-up signal.
According to the embodiments of the present invention, this is achieved by means of a circuit for providing minimum wake-up time that includes a monostable circuit suitable to disable the wake-up signal when said signal has been enabled for a time that is longer than a minimum time established by said monostable circuit and after the input and output signals of the controlled device coincide.
With the embodiments of the present invention it is possible to provide a circuit that guarantees the minimum period in which the wake-up signal remains enabled so that at the end of said period the wake-up signal can go back to the initial state without any delay when the input and output signals of the device being controlled will coincide again.